Study Finds North Atlantic Right Whales Face Higher Collision Risk at Night
A new study published in PLOS One reveals that critically endangered North Atlantic right whales feed closer to the ocean surface at night, increasing their vulnerability to vessel strikes. Research led by Dalhousie University and Ocean Alliance found that while whales stay near the seafloor during the day, they follow zooplankton upward at night, overlapping with ship drafts.
Critically endangered North Atlantic right whales are facing an increased risk of collision with vessels due to a change in their feeding behavior at night, according to a study published earlier this month in the peer-reviewed journal PLOS One. The research indicates that these whales move closer to the ocean’s surface after dark, placing them directly in the path of large ships.
The study was led by Jay Kirkham, a PhD student at Dalhousie University in Halifax, in collaboration with the U.S.-based non-profit Ocean Alliance. The team tagged 23 right whales in the Shediac Valley, an underwater valley in the southern Gulf of St. Lawrence where a portion of the whale population gathers to feed each summer. With an estimated total population of only 384 whales, the species is among the most threatened marine mammals in the world.
Using tags that recorded video footage and movement data, the researchers trained a machine learning algorithm to recognize nighttime feeding behaviors. The findings show a distinct vertical shift in the whales' location depending on the time of day. During daylight hours, right whales typically feed close to the sea floor. However, at night, they follow zooplankton higher up in the water column.
This upward migration creates a dangerous overlap with commercial shipping. Large vessels extend into the water approximately 10 to 15 metres, which coincides with the depth at which the whales are feeding at night. Collisions with vessels and entanglements in fishing gear remain the leading causes of death for the North Atlantic right whale population.
Current protection measures in the region, overseen by Transport Canada and Fisheries and Oceans Canada, include seasonal fishing closures, speed restrictions, and vessel exclusion zones in the Shediac Valley. Despite these efforts, the study found that tagged whales spent approximately 25 per cent of their feeding time outside the designated vessel exclusion zone, exposing them to ship traffic.
Officials have acknowledged the significance of the findings. Fisheries and Oceans Canada stated that the study can help develop tailored management measures to better protect the whales. Meanwhile, Transport Canada noted that its right whale surveillance program uses visual and audio detection tools to support monitoring regardless of daylight conditions, aiming to mitigate risks as understanding of whale behavior evolves.